The conventional telephony network allows users to communicate with each other through a central system of switches, which can be referred to as telephone exchanges. The telephone exchanges provide electrical or optical switches to connect users and allow communication. The conventional telephony network is often referred to as the Public Switched Telephone Network (PSTN). The switches and other equipment necessary to make a connection can be located, for example, in central offices (COs) and in customer premises. The PSTN can have local exchanges that allow a user to call another user of the PSTN through COs of the local exchange. The PSTN can also have long lines that allow long distance call transmission, such that a user can call another user on the PSTN that is not part of the local exchange. In this case, the call may be routed through multiple COs until the call reaches the called party's local exchange.
In recent years, Voice over Internet Protocol (VoIP) has provided an alternative to conventional telephone exchanges. VoIP is the routing of voice conversations over the Internet or other IP-based network. VoIP is a technology that allows a user to make telephone calls using an Internet connection instead of a traditional (analog) phone line connection. VoIP converts the voice signal from a telephone or a computer into a digital signal that travels over the Internet then converts it back at the other end so that a user can speak to anyone with a regular phone number or anyone who also uses VoIP technology. VoIP uses the Internet as the transmission medium for telephone calls by sending voice data in packets using IP rather than sending an analog signal over the PSTN.
Because IP does not provide a mechanism to ensure that voice data packets are delivered in sequential order, or provide any quality of service (QOS) guarantees, VoIP implementations face problems dealing with latency and jitter. Some broadband connections may have less than desirable quality. A momentary drop-out of voice is experienced when IP packets are lost or delayed at any point between the VoIP users. This is a common problem in highly congested networks and/or where there is a long distance routing of the call between end points. Currently, before making a VoIP call, a user is not able to know if the underlying network is able to support a high quality call between the user and the call receiver, wherever the user and the call receiver might be.
With a conventional telephone call, a party is aware of an incoming call when the telephone rings. Currently, when a VoIP call is received via a computer, a window is popped up on the screen on top of all other windows to show that an incoming call is detected. This window has the highest z-order and may obscure other windows that a party already has open. The window remains open until the user takes steps to close it. Such a window for an incoming call is intrusive and interrupts a user from his/her current work.